Method and apparatus for balancing pneumatic tire and support

ABSTRACT

The method of substantially dynamically and statically balancing a pneumatic tire and its support wheel or rim which includes the steps of 1. MEASURING THE DISTANCE THAT SIDEWALL AND/OR TREAD PORTIONS OF THE TIRE EXTEND AXIALLY FROM THE SUPPORT TO DETERMINE ANY DIFFERENCES IN THESE DISTANCES, 2. COMPENSATING FOR ANY DIFFERENCES IN THE DISTANCES BY SECURING A COMPENSATING WEIGHT ON THE SUPPORT DIAMETRICALLY OPPOSITE TO THE GREATEST DIFFERENCE DISTANCE TO THEREBY BALANCE STATICALLY WITH A COMPENSATING WEIGHT, POSITIONED ON THE OPPOSITE SIDE OF THE TIRE SUPPORT IN ALIGNMENT IN AN AXIAL DIRECTION.

United States Patent [72] Inventor Frank 0 Sltidmore [56] References Cited i l'llll'd SL, Cuyahoga FflllS, OhlO UNTED STATES PATENTS 1,240,528 9/1917 Alsworth 33/203.19 l l, N 761 60 5 QR; M526 1968 2,201,982 5/1940 Bazarek 73/4s0x [45] Patented July 2,752,788 7/1956 LaPenta 73/487 confinuafion in pan o applicafion Sen No. 3,303,571 2/1967 Veals 73/146 X 667,573, Sept. 13, 1967, now abandoned.

[54] METHOD AND APPARATUS FOR BALANCING PNEUMATIC TIRE AND SUPPORT 6 Claims, 7 Drawing Figs.

[52] US. Cl 73/66, 33/203. 19, 73/487 [51] lnt.Cl G0lm l/l4 [50] Field of Search 73/459, 66,

Primary Examiner-James .l. Gill Attorney-Oldham & Oldham ABSTRACT: The method of substantially dynamically and statically balancing a pneumatic tire and its support wheel or rim which includes the steps of: (l) measuring the distance that sidewall and/or tread portions of the tire extend axially from the support to determine any differences in these distances, (2) compensating for any ditferences in the distances by securing a compensating weight on the support diametrically opposite to the greatest difference distance to thereby balance statically with a compensating weight, positioned on the opposite side of the tire support in alignment in an axial direction.

PATE sum 2 OF 2 FIG-6 INVENTOR. FRANK o SKIDMORE ATTORNEYS MlE'lll-lltbbl AND APTARATIUS lFOllll ldAlL/tl lCll lG lPhllEtJli/lfit'lllltl 'llllhlE Ahllll SlUlPPUlE LT This application is a continuation'in-part of my application Seri No. 667,573, filed Sept. l3, I967, and now abandoned.

The apparatus for substantially dynamically and statically balancing a pneumatic tire and its support wheel or rim includes a plurality of radially extending arms, roller means on certain of the arms and adapted to engage with the tire support to rotatably support the hub and arms thereon, and gage means mounted on at least one arm to measure the distance that sidewall and/or tread portions of the tire extend axially from the support to determine any difference in these distances.

it is the object of the invention to provide relatively inex pensive apparatus and methods for quickly, with good accuracy, balancing a pneumatic tire and its wheel or rim support both dynamically and statically. Present bubble-balancing or spindle-type balancing equipment can only achieve static balance, not dynamic. in the drawings:

FIG. l is a diagrammatic cross'sectional view of a tire and its support showing areas of dynamic and static unbalance and formulas for effecting balance;

FIG. 2. is a perspective view of one embodiment of apparatus of the invention;

FIG. 3 is an enlarged fragmentary view of a tire support with an associated roller means of FIG. 2;

FIG. t is an enlarged fragmentary crosssectional view of a gage means from FIG. 2', and

FIG. 5 is an enlarged broken away cross-sectional view of a modified embodiment of the invention;

FlG. ti is a plan schematic of the tool of HG. i l which illustrates some other attachments to the basic tool; and

FlG. 7 is a schematic illustration showing how equal balance is achieved in the whole tire, rim, combination using the apparatus and method of the invention.

The schematic showing of Fit}. ll includes a pneumatic tire 10 carried on a support wheel or rim iii. The tire llll is shown with an exaggerated statically out-of-balance tread area w at a distance r from the axis of rotation id. The tire lllll is also shown with an exaggerated dynamically out-of-balance sidewall area W at a distance of R from the axis of rotation Ml. The sidewall area W is at a distance or moment arm A from the center plane in of the tire support l2.

When the tire lid of FlG. l is spun on axis lld the sidewall unbalance area W throws the tire into a dynamically unbalanced condition tending to twist the center plane to to other than a right angle with axis id and causing wobble, bean ing wear, uneven tread wear, and an unsafe driving condition.

To substantially balance the tire of HG. ll dynamically without spinning for almost all practical cases a weight W is secured to the tire support 12 diametrically opposite to the are W. The center of mass of weight W is at a distance R from axis i l and at an axial distance A from center plane to. Therefore, substantial dynamic balance is achieved when since and as the tire is spun on axis Ml all forces tending to tilt center plane in at other than right angles to axis lld are counterbalanced. This assumes, of course, that W is the only weighted area causing dynamic unbalance which is true in most practical tire balancing situations. Naturally, it should be understood that if weight V will cause a greater static unbalance when positioned diametrically opposite area W it should then be placed on the opposite side of the rim as indicated by weight w in FIG. l, as this also follows the formula above.

The amount of weight W to effect counterbalance is a function or factor of the distance of the axially parallel offsetting of area W. in great many cases area W is caused not by faulty sidewall construction of the tire, but because the tire is seated on the rim in a cocked relationship. in other words, the plane of the tire does not coincide with the plane of the rim. This alignment with the rim, and consequent dynamic unbalance. If the distance of the sidewall offset is one-halt inch a larger weight I will have to be used than if the axial offset is only one-eighth inch. in any event, the amount of the axial offset is measured (as hereafter described) and a table is established equating each difference in offset distance to a given weight for selected tire sizes, testing bearing loads dynamically to insure best dynamic balance, and this table, or a series thereof, is supplied with the apparatus to the customer. The computation of the table does not comprise a part of the invention, but depends on the size and characteristics of the tire being balanced and normally is computed by trial and error on the standard tires in each size as made by the major rubber companies.

With the tire in substantial dynamic balance as described the tire id is next tested for static balance on the usual vertical spindle machine. Test weights 70 as seen in FllG. 2, may be utilized to determine the amount and? position of the weight necessary for static balance. Any static out-of-balance may be compensated for by a pair of weights w and W2, one placed on one side of the tire support ill; and the other placed in axial alignment on the other side of the tire support as shown. The weights w and w" are both at a distance r from the axis Ml and are diametrically opposite to the heavy side of the tire and its support. Placing the weights w and W2 equidistant from the center plane to does not upset the previously obtained substantial dynamic balance, but fully compensates to obtain static balance even though dynamic compensating weight W may have upset static balance. A single: weight w, indicated in dotted lines, could be centrally positioned on the rim to take the place of both weights w and w.

Static balance is obtained, accordingly, when Turning now to the apparatus of the invention, a hublike portion MP is generally provided having a shirt 22 which fits slidably down over the vertical spindle ofa conventional spin die-type static balancer for a tire and rim support. A bubble 24 showing true horizontal may be provided at the top of the hub, although this is not necessary since the bubble in the balancer will show through the open top of the hub. The purpose of the bubble on the hub portion Zl'll itself is to help determine if a rim is out of alignment, or if adding weight to compensate for dynamic out of balance changes the static balance condition.

A plurality of arms 2M: extend radially from the hub, preferably at 99 spacing, the arms being calibrated in inches along their lengths. Roller means 22? are mounted on selected arms and include posts Fltl locked in radially equal, but selected position, by setscrews 32. A calibrated rod 34 is slidably received in each post Eltl and is locked by setscrew 36 at selected height therein. Each rod 34 rotatably carries a ball bearing at its lower end adapted to roll upon the bead retaining flange 4d of a tire support 423 (See FlG. 3) when the apparatus is mounted on the vertical spindle-type tire balancer, as aforesaid. Note however, that the apparatus could have only one arm carrying both roller means 2% and gage means so long as it carries a circular shirt to sliclably engage over the spindle.

in the preferred embodiment of the invention, gage means do are mounted on at least one arm an. The arms 26a are preferably longer than arms Mi are diametrically opposed to each other and situated midway between adjacent arms 226. Also arms Eon are curved at Ebb to allow the arms to follow the contour ofa pneumatic tire. The gage means do includes a block dill secured in radially selected position with a setscrew Eitll. A calibrated rod 52 extends siidably through the block, and is either locked in position in the block or given a selected friction by a spring 5d secured to the block and adjustably forced into contact with the rod by thumbscrew 56, all as best seen in MG.

The rod 52. may be rounded at its lower end to engage with a selected area of the sidewall or tread of the tire, or may have a cup secured thereto with setscrew (all, the cup receiving In the operation of the apparatus described, with the hub 20, slidably received over the vertical spindle of a tire balancer, the posts 38 are adjusted to bring rollers 38 into contact with the bead flange 40 (FIG. 3) so that the entire apparatus of FIG. 2 can be rotated on the support 42 of the tire and the support being tested. Normally, skirt 22 will center the apparatus with respect to the bead flange 40, but with a minimum of two arms skirt 22 is not necessary if the rollers engage against the shoulder of the bead flange 40, as seen in FIG. 3. It should be understood that substantial dynamic unbalance can be determined without a static bubble balancer by the device of the invention rolling around the bead seat of the tire support rim. For plastic or nonferrous supports 42 the flange 40 may not have a shoulder, however, making use of the skirt 22 necessary for central positioning of the apparatus with respect to the spindle of a static balancer regardless of the number of arms 26. Substantial dynamic balance has been achieved under controlled testing conditions utilizing the device of the invention described above.

Now at least one gage block 46 is adjusted to bring rod 52 over the sidewall or at the side of the tread of the tire under test and just into contact therewith. Thumb nut 56 provides light friction on the rod 52 allowing it to slide. The apparatus of FIG. 2 is rotated through at least 180 and axially offset side areas of the tire are either marked with chalk 62,' or the distance of offset is measured by rod 52 sliding in block 48 or both. Once the distance of offset is known (such as area W) the proper weight W can be selected and applied diametrically opposite thereto to achieve dynamic balance. The amount of weight is dependent on the amount of axial offset, and the size and characteristics of the tire. I

It is preferable to substantially dynamically balance both sides of the tire and its support in the manner described. In also all instances, it will be found that the opposite sides of the tire are 180 out of phase with respect to substantial dynamic balance so that the weights necessary to achieve substantial dynamic balance for both sides of the tire will statically cancel each other.

Next static balancing is effected as heretofore set forth, the bubble 24 facilitating this operation. However, to determine the amount of weight necessary for static balance the invention contemplates that small individual test weights 70, as seen in FIG. 2 of the drawings, might be slidably positioned by hand, on one of the arms 260, with 260 in the proper radial direction. The weights 70 may be of various increments of weight, and one or more may be used and positioned in any radial relation on arm 26a until by trial and error with one or more test weights 70, the desired static balance is achieved. Normally, the weight or weights 70 are positioned in the same radial relation as the permanent weights which will be attached to the rim.

Also, note that the gage block 46 can be adjusted so that rod 52 might measure the radial out-or-round of the thread, as well as the axial displacement.

It should also be noted that the gage block 46 can be adjusted so that rod 52 might measure the axial distance from the rim on both sides to the point of attachment of the center support web of the rim defining the plane of rotation of the tire, rim, wheel combination, so that dynamic balance might be maintained where there is a difference in these axial distances, (especially true on the wide tread tire designs utilized today) by placing more weight when statically balancing with clip-on type weights on the side of the rim with the shorter distance to the support web defining the plane of rota tion of the tire, rim, wheel combination. It has been found that the plane of rotation defined by the attachment point of the web normally carries the center of gravity of the rim and wheel when measured with the rim and wheel in a vertical plane. Therefore, it is usual in practicing the method of the invention to properly distribute clip-on type weights during the static balance so as to not disturb the previously determined substantial dynamic balance. Normally this will require positioning of a greater amount of weight on the outboard flange of the rim, than on the inner flange since the attachment point for the web of the rim is closer to the outboard flange than the inboard flange in the usual wheel rim combination.

FIG. 5 illustrates the arm arrangement of a modified embodiment of the invention which though operating the same, is a little different structurally. Specifically, in this embodiment, a pair of rods and 102 are telescoped with relation to each other and held in a proper length position by appropriate cotter pin 104 to form each of the arms. A roller 106 is mounted to the end of rod 100 in fixed position by an appropriate lock washer 108. The roller 106 rolls on the rim 110 in the same manner as the roller 38 rolling on rim 40 as indicated in FIG. 3 of the drawings.

In this embodiment, however, a test is made for the roundness or trueness of the rim itself, and this is made by an adjustable sleeve 112 slidably received on rod 100 and held in position by an appropriate locking screw 114. The sleeve 112 has a downwardly projecting pin 114 extending from the bottom thereof which is adjusted so as to be in close adjacent relationship to the rim 110, as illustrated. Hence, it should be understood that upon rotation of the tool, and the arm established by rods 100 and 102, the trueness or circular roundness of the rim 110 will be measured by pin 114. Any major deviations, of course, will either have to be corrected, or will indicate that the rim is unacceptable for high speed automobile passenger tire operation.

FIG. 6 illustrates a plan view of the tool shown in FIG. 5, and illustrates four posts 102 spaced at 90 to each other and held to a center hub 102a which is received around the spindle of a static balancing machine, as has been described above. However, FIG. 6 also illustrates a pair of arms and 122 mounted in 180 relation to each other on hub 102a. They are positioned at 45 relation between adjacent arms 102, and serve to measure lateral tread displacement for dynamic balancing as described above. Each arm 120 and 122 mounts a plate 120a and 122a on which weight may be placed to determine the proper amount to statically counterbalance the heavy area designated at 124. The plates 120a and 122a operate in coordinator with arms 102 and pointers 126, 128, I30, and 132 mounted thereto. In effect, each arm 102 marks a point on the rim in 45 relation on each side of arms 120 and 122. The pointers 126 and 128 mark a point on the rim in 60 relation on each side of arm 120 while pointers 130 and 132 mark a point on the rim in 60 relation on each side of arm 122.

The static balancing procedure with the tool is to place the hub 102a over the hub of a static balance device, and then to place either arm 120 or 122 so it lies over the center of gravity of the heavy area. This is followed by placing weight onto the respective plate on the opposite arm until static balance is achieved. Note that the plates 120a and 122a are marked with 0, 30, 45, and 60 designations. This means that weights piled on the plate adjacent the respective designation, when the bubble on a static balance device indicates proper balance, can be divided exactly in half, with half mounted to the rim at the specific angular designation from the plate indicated. However, it should also be understood that the amount of weight necessary to counterbalance at 0 can also be applied directly at the 60 indication by the respective pointers 126 and 128, or 130 and 132 depending on which arm is utilized without making the special determination adjacent the 60 indication on the plate.

The optimum balance in a tire/wheel combination achieved by an equilateral balance such as the 120 relationship indicated in FIG. 6 of the drawings is shown in schematic form in FIG. 7. Specifically, this figure shows a relationship between a tire I30 and a rim 132 such that the tire has a radius R and the rim has a radius 12/2. A 4 ounce heavy area at 134 will require 8 ounces balancing compensation weight at points 136 and 138, respectively, on the rim at 120 spaced relationship from the radial position of the 4 ounce out-of-balance area 134. This generates an equilateral triangle illustrated by a solid line M0 and means that equal thrust will prevail throughout the entire tire/rim combination due to centrifugal force during rotational operation of the tire. This uniform distribution of weight means that exactly 4 ounces of thrust will be present at each of the 60 points marked around the periphery of the tire during rotational operation thereof. This can very greatly eliminate rough ride due to unequal radial or circumferential force distributions in the tire because of the unequal balance around the entire tire combination that may be present if a single lumped weight is utilized opposite the 4 ounce heavy area 124.

It is also possible utilizing the tool shown in FIG. 6 of the drawings to determine whether the heavy area 124 is spread over a long arcuate section of the tire, which is normally the case because of shifting of the tire during molding, or whether the heavy area 124 is localized due to some local condition such as a radial lap splice, or some heavy localized condition within the rubber compounding itself. The technique to determine this relationship is to simply determine the exact amount of weight necessary to counterbalance the heavy area 124 on both plates 12Gb and 122b. The amount of weight necessary to counterbalance on plate 120!) will be the same regardless of whether the heavy area is distributed or localized at 124. However, on plate 122b, it will be found that less weight is necessary to counterbalance at the 45 points shown by arms 122 and 1220 when the heavy area 124 is spread over a longer arcuate distance than the heavy area is localized. A table can easily be made up to allow the operator of the tool to utilize this determination as to the extent of the heavy area being spread or calized, or it can be of great value to the factory to enhance quality control procedures. The proof of this method is quite easily accomplished by simply placing weights on the tire during use of such tool in either a localized heavy area or a spread heavy area, and actually counterbalancing on the 45 relationship with arms 122 and 122a, to show that different amounts of weight are necessary to counterbalance at the points designated by arms 122 and 122a, even though exactly the same amount of weight on plate l22b will indicate the counterbalance with the weight localized at 124 or spread out over a long arcuate distance.

Hence, it should be understood that the tool of the invention in combination with the balancing method described achieves the following improved features:

1. Can determine static balance on even an improperly operating static balance machine by use of the circular level placed over the center hub.

2. Can determine a warped rim by the four equal arms rolling around the rim. If the rim is warped, the arms will not contact equally and the warp can be detected.

3. Can determine out of round rims by the pins 114 extending down from the arms. Either one or more pins may be utilized on one or more of the arms.

4. The device can determine if the tire is out of balance over a long crescent area or a condensed area by means of the arms 102 and the 45 designation on either plate 120a or 122a.

5. The device locates the weight to the correct position for equilateral balance and equal centrifugal force thrust in the rotating tire by determining the correct amount of the weight and the position thereof by means of arms 122 and plates 120a and 122a.

6. The device locates dynamic unbalance in the majority of tire cases where lateral disproportionates may exist in the tread or sidewall of a tire and corrects for these unbalances with a properly positioned weight.

7. The device determines out-of-roundness in tires by an appropriate adapter to one of the measuring arms.

While in accordance with the patent status only one best known embodiment of the invention has been illustrated and described in detail, it is to be particularly understood that the invention is not limited thereto or thereby but that the inventive scope is defined in the appended claims.

What i claim is:

1. That method of substantially dynamically and statically balancing a combination pneumatic: tire and its support assembly which includes the sequential steps of 1. measuring the distance that sidewall and/or tread portions of the tire extend axially from the support and marking any area of lateral displacement.

2. mounting the assembly on a static tire balance apparatus and positioning compensating weight on the support assembly in an amount proportionate to the distance of lateral offset so as to provide a resultant compensation at a point directly or diametrically opposite such areas so as to have the least detrimental effect to the static balance of said assembly as measured by the balancing apparatus, and

. compensating for any remaining static out-of-balance by securing compensating weight to the assembly as determined by the balance apparatus.

2. That method according to claim 1 wherein step l is performed on both sides of the tire before proceeding with steps (2) and (3) and where step (2) is followed for each area of lateral offset.

3. That method defined in claim 1 wherein the calculation of the amount of weight and position necessary to achieve the final static balance of step (3) includes positioning equal amounts of weight 120' on each side of the center of the heavy spot of the tire on its support rim split so that half of each equal amount of weight at such 120 position is attached on each side of the support rim to statically balance the tire.

4. Apparatus for measuring axial ofi'set of a pneumatic tire and its support wheel or rim which includes a hublike portion, at least three arms extending radially from the hublike portion at substantially equally spaced angular intervals, roller means mounted on said arms and adapted to engage with the tire support to rotatably support the hub and arms thereon, and establish a reference plane, and gauge means mounted to at least one of said arms to measure the distance that sidewall rim and/or tread portions of the tire extend axially from the support to determine any lateral difference in these distances from the plane of the arms around the circumference of the tire.

5. The combination defined in claim 4 wherein the hublike portion includes a skirt adapted to fit down over a vertical spindle of a static tire balance machine, and a bubble device on the hublike portion showing levelness of the tire and its support wheel assembly.

6. The apparatus defined in claim 4 which includes four arms at intervals, and pointers with tips attached to adjacent arms at 90 relation to each other and having the tips thereof pointing to the support at 60 relation on each side of a line bisecting such arms, an arm positioned on the line bisecting such adjacent arms, and a flat plate mounted to the last said arm on a line between the tips of such pointers and the tips of such adjacent arms. 

1. That method of substantially dynamically and statically balancing a combination pneumatic tire and its support assembly which includes the sequential steps of
 1. measuring the distance that sidewall and/or tread portions of the tire extend axially from the support and marking any area of lateral displacement.
 2. mounting the assembly on a static tire balance apparatus and positioning compensating weight on the support assembly in an amount proportionate to the distance of lateral offset so as to provide a resultant compensation at a point directly or diametrically opposite such areas so as to have the least detrimental effect to the static balance of said assembly as measured by the balancing apparatus, and
 3. compensating for any remaining static out-of-balance by securing compensating weight to the assembly as determined by the balance apparatus.
 2. mounting the assembly on a static tire balance apparatus and positioning compensating weight on the support assembly in an amount proportionate to the distance of lateral offset so as to provide a resultant compensation at a point directly or diametrically opposite such areas so as to have the least detrimental effect to the static balance of said assembly as measured by the balancing apparatus, and
 2. That method according to claim 1 wherein step (1) is performed on both sides of the tire before procEeding with steps (2) and (3) and where step (2) is followed for each area of lateral offset.
 3. That method defined in claim 1 wherein the calculation of the amount of weight and position necessary to achieve the final static balance of step (3) includes positioning equal amounts of weight 120* on each side of the center of the heavy spot of the tire on its support rim split so that half of each equal amount of weight at such 120* position is attached on each side of the support rim to statically balance the tire.
 3. compensating for any remaining static out-of-balance by securing compensating weight to the assembly as determined by the balance apparatus.
 4. Apparatus for measuring axial offset of a pneumatic tire and its support wheel or rim which includes a hublike portion, at least three arms extending radially from the hublike portion at substantially equally spaced angular intervals, roller means mounted on said arms and adapted to engage with the tire support to rotatably support the hub and arms thereon, and establish a reference plane, and gauge means mounted to at least one of said arms to measure the distance that sidewall rim and/or tread portions of the tire extend axially from the support to determine any lateral difference in these distances from the plane of the arms around the circumference of the tire.
 5. The combination defined in claim 4 wherein the hublike portion includes a skirt adapted to fit down over a vertical spindle of a static tire balance machine, and a bubble device on the hublike portion showing levelness of the tire and its support wheel assembly.
 6. The apparatus defined in claim 4 which includes four arms at 90* intervals, and pointers with tips attached to adjacent arms at 90* relation to each other and having the tips thereof pointing to the support at 60* relation on each side of a line bisecting such arms, an arm positioned on the line bisecting such adjacent arms, and a flat plate mounted to the last said arm on a line between the tips of such pointers and the tips of such adjacent arms. 